Method of compacting powdered resin into slots of magnetic cores

ABSTRACT

Apparatus for shaking and compacting heat-hardenable powdered resin into interstices between coil windings in a slot of a core of magnetic material, including a vibrating perforated table, clamps adjustably mounted on the table for holding a core in place with the slot in vertical position, a vibrator mounted under the table for shaking the core vertically, and a hopper under the table for collecting excess resin when powdered resin is spread over the upper open ends of the slot.

States Patent lfiipple et al.

[4 1 Sept, 9, r975 METHOD OF COMPACTING POWDERED RIESlN llNTO SLOTS OFMAGNETlC CURlES Inventors: llarry l. lfiipple, Pittsburgh, Pa.;

Virgil ,l. Cozzarin, Clarence, N.Y.; Francis C. Kapperman, deceased,late of Eggertsville, N.Y., by Dorothy M. Kapperman,

administrator Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

Filed: Mar. 30, 1973 Appl. No.: 346,533

Related US. Application Data Division of Ser. No. 71,933, Sept. 14,1970, Pat. No. 3,752,1 16,

llnt. Cl B2811) 1/08 Field 011 Search 117/18, 20, 21, 161 R, 117/161 ZB,62; 118/57, 308, 406, 425, 408; 425/456; 264/71, 272

and 1 '1 1 1 11 1 m a a [56] References Cited UNITED STATES PATENTS754,581 3/1904 Magnus 117/20 3,030,597 4/1962 Piaia, Jr. et a1...264/272 3,261,707 7/1966 Korski et al. 1 18/406 3,549,582 12/1970 Payneet a1. 117/161 ZB Primary Examiner-Charles E. Van Horn AssistantExaminer-Jerome W. Massie Attorney, Agent, or FirmR. D. Fuerle [5 7ABSTRACT Apparatus for shaking and compacting heathardenable powderedresin into interstices between coil windings in a slot of a core ofmagnetic material, including a vibrating perforated table, clamps adjustably mounted on the table for holding a core in place with the slot invertical position, a vibrator mounted under the table for shaking thecore vertically, and a hopper under the table for collecting excessresin when powdered resin is spread over the upper open ends of theslot.

2 Claims, 2 Drawing Figures PATENTEDSEP' 1 1 3, 904-, 724

'HHH (mu FIG I 78 if MUFFLER 80 MUFFLER 9 90-"lOOp sI SUPPLY wyw FIG. 2

METHOD OF COMPACTING POWDEREI) RESIN INTO SLOTS OF MAGNETIC CORES CROSSREFERENCE TO RELATED APPLICATION This application is a division of S.N.71,933, filed Sept. 14, 1970, now U.S. Pat. No. 3,752,116. Thisinventionis related to application Serial No. 61.106, filed Aug. 5, 1970 now U.S.Patent 3,710,437.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to apparatus for shaking powdered resinous material intointerstices located between coil wires and between coil wires and sidewalls forming slots of a core of magnetic material, whereupon subsequentheating the powdered resin is fluidized and cured in place in order toavoid the existence of cavities within the core slot.

2. Description of the Prior Art Rotating electrical apparatus such asmotors and generators, employ insulated coils comprising central coreportions and end turn portions. The preparation of coils, windings, orconductors for insertion into slots of magnetizable cores by priormethods has involved the time-consuming and costly process of applyinginsulation tape, wrappers, and slot cell liners to the coil portions,such as disclosed in U.S. Pat. No. 3,054,880. The process wasparticularly involved where it was employed in the repair of coils formotors and generators.

A method that would eliminate or reduce the amount of taping andwrapping required on all types of rewound rotating apparatus would bedesirable. In addition to reducing the labor required in the rewindingof the coil windings, a reduction of subsequent treatment cycles hasbeen sought. More particularly, in the area of form-wound coils forstators, rotors, and armatures, with, for example, direct current fieldsand rotating fields, the methods remain the same; i.e., mostlyhandtaping of the assembled conductors, varnish treatment, andapproximately 12 hour baking cycles.

The foregoing problems are of greater moment where repair shops for suchapparatus are involved. Repair shops handle apparatus of various sizesand are therefore necessarily faced with a wide variety ofnonstandardized coil shapes and sizes and different varnishes requiringdifferent applying and curing procedures. For example, repair shops mustbe prepared to handle components of rotating apparatus varying indiameter from about 6 inches up to 6 feet or more. In suchcircumstances, the methods employed must be adapted to a maximum outputat a minimum cost.

SUMMARY OF THE INVENTION It has been found in accordance with thisinvention that the foregoing problems may be overcome by winding coilsinto the slot of a core of, for instance, a stator, packing theinterstices between the coils and core walls with powdered fusible resinmaterial of fine mesh by vibrating or shaking the stator while pouringthe powdered resinous material onto the open top ends of the slots sothat the material descends into the slot and fills the intersticesbetween the conductors and the core walls where the powder particleslodge and become compacted in place and accumulate until all voids andcavities are filled, whereupon the assembly of the stator and the resinfilled slot is ready for a subsequent heating operation in order to fuseand cure the resinous material in place.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional viewshowing the shaker device with a stator of an electric motor mounted inplace; and

FIG. 2 is a schematic view of the air system used for operating theshaker device.

DESCRIPTION OF THE PREFERRED EMBODIMENT The device of the presentinvention is generally indicated at 10 in FIG. 1. It includes a base 12,a hopper 14, a vibrating table 16, clamp means 18 for holding aworkpiece, such as a stator 20 fixedly in place, and a vibrator 22. Thedevice 10 may have any peripheral shape such as circular or rectangular,so long as it is suitable for accommodating stators 20 of any sizeranging from as low as, say, about 6 inches up to 40 inches or greaterin diameter. The preferred general configuration of the device 10 is asquare in the plan view which is the configuration shown in FIG. I whichis a vertical sectional view, taken diagonally of the square.

The base 12 is preferably composed of metal channel members 24 of whichthere are four disposed in two parallel pairs on opposite sides of thedevice 10. Adjacent pairs of members 24 are secured together at theircorners, such as by welding, to form a rigid square base. At each cornera leg 26 is disposed below the channel members 24 and a grooved wheel orcastor 28 is provided under each leg. Thus, the device 10 may be mountedon a pair of tracks for movement between two or more work positions,such as placement of the base under a crane or hoist for lifting aworkpiece of stator 20 in place and subsequently moving the device 10away from the area under the crane.

The hopper 14 includes inclined plates 30, the upper peripheral portionsof which are attached to the upper side of the base 12. The lower endsof the inclined plates 30 are provided with a discharge spout 32 havingsuitable valve or gate 34 for emptying the hopper of excess powderedresin 36 when a sufficient amount of the resin accumulates in the hopper14.

The vibrator table 16 includes a perforated plate 38 having a pluralityof openings 40 through which the excess powdered resin 36 passes fromthe stator 20 to the hopper 14. A peripheral flange 42 extends aroundthe outer edges of the plate 38. The plate 38 is mounted on suitablesupport members which may be a pair of crossed I-beams 44 each of whichextends diagonally from opposite corners of the device 10. The outerextremities of each support member or beam 44 is supported by a leg 46such as a metal angle member the upper ends of which legs are secured tothe beams 44 in a suitable manner such as by welding (not shown).

As shown in FIG. I, the upper portion of the device 10 including thevibrator table 16 is separated from the lower portion of the deviceincluding the frame 12 by elastic or resilient mounting means at eachcorner including elastic connectors 50 composed of rubber or similarmaterial in order to facilitate the vibration of the table 16 and toprevent the base 12 from having a dampening effect upon the vibration.Particularly good results have been obtained when the conductors 50 areinflatable cushions having internal air pockets 52 which are filled withcompressed air at a pressure of such as 150 pounds per square inch bysimilar air conduits 54 leading from a source of supply of compressedair. The upper side 56 as well as the lower side 58 of the airconnectors 50 are secured to the adjacent metal plates 48 on the topside and 60 on the lower side by vulcanizing in a manner well known inthe art.

When the device is not in use, the air connectors or cushions 50 aredeflated so that the lower ends of the legs 46 rest upon support blocks62 which are mounted on the channel members 24. As a safety member, eachblock 62 has a flange 64 which extends upwardly and adjacent to thecorresponding leg 46 for maintaining the table 16 in alignment with thebase 12, as shown in the drawing.

The clamp means 18 includes a plurality, and preferably four, chuck-likeclamps that are adjustably mounted on separate guide ways 66. Each guideway 66 extends from one corner of the table toward the center of thedevice 10. The guide ways 66 are mounted on and supported by the supportmembers 44. Each clamp is movable along its corresponding guide way 66which includes a bolt-receiving groove (not shown) of conventionalconstruction in which the head of bolts 68 are disposed. Each bolt 68 istightened in place by a nut 70 when the clamp is in a position proximateto the mounting position of the stator 20. In addition, each clampincludes a clamp jaw 72 having a lower portion which is threadedlyadjustable within the clamp and for mounting the stator 20. For thatpurpose, each jaw includes a stator support surface 74. As the result ofthe several clamps 18 a stator ranging in size from about 6 inches up toabout 40 inches in diameter may be mounted on the device 10 forintroducing and packing powdered resin 36 in place in the core slots.

For that purpose the vibrator 22 is attached by a plurality of bolts 76to the undersurface of the support members 44. Good results were hadusing a vibrator 22 of the type having a reciprocating piston within acylinder from which compressed air is exhausted alternately through airoutlets 78 and 80 and in which air is applied through an air inlet 82.The speed at which the piston reciprocates vertically within thecylinder is dependent upon the air pressure involved. For example, at 10pounds per square inch of air pressure, the piston reciprocates at afrequency of about 540 cycles per minute while at 100 pounds per squareinch of air pressure, the piston reciprocates at about lllO cycles perminute. The vibration is transmitted to the support members 44 and theclamps to the stator 20. Other mechanisms for vibrating the table 10,may be employed in place of vi brator 22. Thus a verticallyreciprocating solenoid can be substituted therefor. The direction of thevibration should be parallel to the axis of the stator or rotor slots.In one test the table 10 was vibrated with a rocking mechanism and farless satisfactory results were obtained than with vibration in thedirection parallel to the stator axis. The frequency may vary from thatgiven above, namely 540 to l l 10 cycles per minute, at which excellentresults were obtained to as little as 100 cycles per minute to as muchas 100 cycles per second.

As shown in FIG. 2, the schematic layout of the air system for operatingthe connectors or inflated cushions 50 as well as the vibrator 22,includes conduits 54 leading to the connectors 50 through a feed linethrough a source of air supply which may preferably be in the range offrom about 90 to 150 psi. The air supply 82 for the vibrator leads tothe same air supply. Each air supply is provided with suitableindividual valve control means in a manner known in the art. Manystators were treated in the apparatus of the present invention, andtests and inspection of the cores after filling and even curing showedexcellent insulation with the coils being well bonded.

During vibration, a supply of powdered resin 36 is placed on the topside of the stator 20 with the slots 84 extending vertically, and theresin particles drop downwardly through the several core slots 84 inwhich coil windings 86 have been previously mounted. To prevent thepowdered resin 36 from dropping through the central armature or rotoropening in the stator 20 an inflatable bladder 88 having an air inlet 90is placed in the center of the stator and inflated so that it pressesagainst the core walls. In addition, a suitable wall 92 comprising, forexample, metal foil is wrapped around the outer surface of the end turns94 of the coil windings 86 to prevent the powdered resin 36 fromspilling over the outer periphery of the stator 20.

As a result, during the vertical vibration of the table 16, theparticles of powdered resin 36 move down wardly into the interstices andopenings between the vertical portions of the coil windings 86 as wellas adjacent to the walls forming the core slots 84 until the entire voidspace is filled with powder. During the preliminary part of the shakingoperation a substantial portion of the particles of powdered resin 36drop through the stator and are collected in the hopper 30.Subsequently, as the particles gradually fill in the spaces, wedgeagainst each other and are compacted in place, they gradually build up abarrier against continued free movement of the resin through the statorslot. It is often desirable after the slots appear to be filled from theone end, the stator 20 may be turned over and powdered resin 36 may bevibrated through from the opposite end of the windings until the entirefree volume of all of the slots 84 is filled.

Thereafter, the assembly of the stator 20 with its windings 86surrounded with a compact filling of the powdered resin 36 within theslots 84 is removed from the device, placed in an oven and heated to asuitable temperature where the particles of resin 36 become fused andsubsequently cured in place. In some cases the windings may be energizedwith electrical current to a temperature high enough to fuse the appliedpowdered resin.

Rotors or armatures may be similarly treated, except that an outershield or inflatable tube can be placed around the outer periphery toenable resin powder to flow only into the slot.

Accordingly, the device of the present invention provides a device formounting a stator or rotor and filling the core slots therein with asuitable powdered insulating material under vibration. The insulatingmaterial is preferably a powder comprising a heat hardenable resin.Exceptionally good results were had with a blend of an epoxy resin, andamine curing agent, and a silicon filler. A composition comprising 90parts by weight of a potentially reactive epoxy resin, with 5% by weightof dicyandiamide, and 10 parts of silica of a fineness averaging 1microns, was milled on hot rolls to form a uniform molten dispersion,without reaching a thermoset condition, cooled and powdered to aparticle size wherein substantially all of the resin passed through amesh sieve, and over 90% was retained on a mesh sieve. Procedures formaking such compositions are set forth in US. Pat. No. 3,039,987.

Numerous other powdered resinous compositions may be employed. Thecompositions may comprise all resin with little or no fillers, or mayinclude up to or more of finely divided fillers such as iron oxide,alumina, titanium dioxide, and finely divided mica, or mix tures of twoor more. While epoxy resins have given good results, other hardenableresins may be substituted in whole or in part therefore. Other catalystssuch as acid anhydrides may be employed. The powdered resinous materialis preferably fusible at a temperature of from about 150F to 350F.

The resin composition can be ground to a fine powder which is screenedto remove excessively coarse particles. A screened resin compositionpowder that passes through a 60 mesh screen (designated a 60 mesh powder) will contain particles of various sizes, all passing through the 60mesh sieve, includes some that will pass through a 200 mesh sieve, whilea high proportion will be retained on this 200 mesh sieve. Good resultshave been obtained with 40 mesh, 60 mesh and 100 mesh powders. Powdersof 150 mesh and 200 mesh can also be used.

The foregoing procedure and apparatus may be applied for insulatingcoils in stators of electrical equipment of varying sizes, ranging fromabout 6 inches to 6 feet in diameter an .svice being energized withupwardly of 3000 vol' The invention has been applied to both stators andre :rs of many sizes and shapes with excellent results.

it is understood that the above specification and drawings are merelyexemplary and not in limitation of the invention.

What is claimed is:

ll. A method of packing a heathardenable resin in the form of anon-fluidized powder into the slots and spaces of stators of varioussizes comprising:

1. positioning a stator with its slots in a substantially verticalposition;

2. pouring said resin into the top of said slots and spaces;

3. vertically vibrating said stator until said resin has substantiallyfilled said slots and spaces to the extent that said slots and spacesare substantially fillable from the top;

4. halting said vibration;

5. turning said stator upside-down;

6. repeating steps (2), (3) and (4); and

7. heating said stator to fuse and cure said resin.

2. A method according to claim 1 wherein the frequency of said vibrationis 200 to 6000 cycles per min-

1. A METHOD OF PACKING A HEATHARDENABLE RESIN IN THE FORM OF ANON-FLUIDIZED INTO THE SLOTS AND SPACES OF STATORS OF VARIOUS SIZESCOMPRISING:
 1. POSITIONING A STATOR WITH ITS SLOTS IN A SUBSTANTIALLYVERTICAL POSITION,
 2. POURING SAID RESIN INTO THE TOP OF SAID SLOTS ANDSPACES,
 2. pouring said resin into the top of said slots and spaces; 2.A method according to claim 1 wherein the frequency of said vibration is200 to 6000 cycles per minute.
 3. vertically vibrating said stator untilsaid resin has substantially filled said slots and spaces to the extentthat said slots and spaces are substantially fillable from the top; 3.VERTICALLY VIBRATING SAID STATOR UNTIL SAID RESIN HAS SUBSTANTIALLYFILLED SAID SLOTS AND SPACES TO THE EXTENT THAT SAID SLOTS AND SPACESARE SUBSTANTIALLY FILLABLE FROM THE TOP,
 4. HALTING SAID VIBRATION, 4.halting said vibration;
 5. turning said stator upside-down;
 5. TURNINGSAID STATOR UPSIDE-DOWN,
 6. REPEATING STEPS (2), (3) AND (4), AND 6.repeating steps (2), (3) and (4); and
 7. heating said stator to fuse andcure said resin.
 7. HEATING SAID STATOR TO FUSE AND CRUDE SAID RESIN.